Stump heights and sprouting of European aspen, pubescent and silver birches, and damage to Norway spruce and Scots pine following mechanical and brush saw cleaning
Results of precommercial thinning (cleaning) by brush saw and by a machine-mounted device, consisting of a hydraulically-driven heavy disc with two short steel flails mounted in a journal bearing, are presented. Plots were laid out in middle and south Sweden in 1983, some being observed annually until 1989. There were significant differences between the two methods as regards the number of sprouts on European aspen (Populus tremula L.) and birch (Betula pendula Roth and Betula pubescens Ehrh.) stumps six years after cleaning. Plots cleaned by machine had a larger number of birch or aspen sprouts, than plots cleaned by brush saw. Mean height of stumps was significantly greater on plots cleaned by machine. Stumps cleaned by machine under snow conditions were 30-70 cm high. There were no significant differences in the number of sprouts or in the height of sprouts, between high and low stumps. Cleaning by machine damaged 7-13 per cent of conifers classified as main stems, as compared to no damage caused by brush saw cleaning. Practical recommendations are given: cleaning by machine under a snow cover is not recommended in most cases.
Betula pendula; Betula pubescens; Populus tremula; Pinus sylvestris; Picea abies; sprouts; stump height; growth, damage; mechanical cleaning; brush saw
Studia Forestalia Suecica
Publisher: Faculty of Forestry, Swedish University of Agricultural Sciences
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